Re: Kuhne 24 GHz transverter IF


Chris Bartram G4DGU
 

Hello Neil

I have a totally Kuhne-free station and always have had. So I'm free to choose my IF levels - which on TX are 144MHz/0dBm (from guess where !!!) on 10368, and 438MHz on 24048 obtained by carefully up and down converting 38MHz.   144 does present a few problems,  largely due to potential breakthrough and radiation problems asI'm near a flight path to Newquay Airport and try to be responsible.These which are eliminated  byusing decent coax (FSJ2/50) for the IF runs from my shack to the dish. If I wanted to generate more IF power, I know how to achieve very high linearities, but that would be a bit too much like the work I retired from!

You might explain to the PNRs that the reason why we are not sampling microwaves directly, is because it's freakingly expensive to do so. It can be done, but not by the usual monolithic offerings of the semiconductor industry. Perhaps you should challenge them to come-up with a 14 or 16bit sampler capable of directly sampling 10GHz! As I said the other day, most so-called 'SDRs' consist of a relatively low-frequency sampling back-end, preceeded by an image reject up-down converter. That's exactly what we are doing with our FDM-DUOs and transverters; using a better sampler than is contained in most 'SDRs' and certainly very much better up-down converters!

'The semiconductor industry is rather good at generating hype and sometimes quite adequate at product design!'

73

Cynical of mid-Cornwall aka Chris G4DGU


On 19/08/2020 15:58, Neil Smith G4DBN wrote:

My current episode of grumpiness was triggered when some (relatively) young tech hobbyists gave me incredulous stares when I tried to explain why all the pics of microwave activity are folks in laybys with dishes on tripods rather than the cool and exciting stuff they had been expecting.  It is all very nice, and I don't mind a bit of that myself, but it doesn't seem to inspire potential new recruits, who know about SDRs and deep tech, but haven't heard of superhets and are only vaguely aware of the existence of quaint old radio designs which aren't digital, system-on-chip and software-defined.

I tore the lid off my MKU23 G4 the day it arrived, and swapped the dropper resistor, but there isn't exactly any spare space to fit an IF RX socket without serious microsurgery. The alternative is to go REALLY old-school and build a gasfet waveguide preamp and use one or two of Kuhne's ancient PCBs to make a last-century-tech transverter, seeing as I'd have to muck about with implementing an LO anyway.  I'd have to machine up some very good cavity filters, but I know a man with a mill. Doing something more sensible with nice modern up/downconverter chips is a step too far in terms of time expended versus results achieved.

Andy's right though, I should just hold my nose and sort out a very linear 2m booster amp and send Kuhne all my pocket-money, horrible though that solution might be. At least then I could sell the un-butchered Kuhne if I ever get round to making something spiffy.  Or if Kuhne come up with a G5 with separate low-level IF input.

Neil G4DBN

On 19/08/2020 14:57, John Lemay wrote:

Neil

 

Before you get Really Grumpy (darn it, too late!), try the transverter out; Gear that I have from Kuhne requires much less drive than stated, so you may be in luck. Admittedly, I’ve no experience of the 24GHz unit.

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Neil Smith G4DBN
Sent: 19 August 2020 14:45
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Kuhne 24 GHz transverter IF

 

Just because it is popular, doesn't make it less weird though. Just seems like adding unnecessary transmit IMD. I can't imagine a use-case where I'd want to key the transverter from a rig rather than a sequence controller, but I suspect the primary application for their 24 GHz stuff is lovely sepia-tinged nostalgic retro tripod-on-a-hilltop-with-an-817 speakymode rather than EME or home-station terrestrial digimodes with SDRs and it is me that is out of step with commercial reality as usual.

Neil G4DBN

 

On 19/08/2020 14:25, Andy G4JNT wrote:

A single IF port, I guess, is a strongly preferred option, and carrying PTT control with it.   That has become a de-facto standard.   Level, well, yes, it's annoying, but 500mW isn't that much to generate.   Two devices instead of one from the mixer/source, but gain is cheap.

 

Andy

 

 

 

On Wed, 19 Aug 2020 at 14:14, Neil Smith G4DBN <neil@...> wrote:

I asked Kuhne if they could modify the 144 MHz IF input on their 24GHz
transverter so I could drive it with 10-15 dBm, but they declined. I
guess the majority of customers must still be using ancient superhet IF
radios and don't see anything perverse about generating 0.5 to 5W at
144MHz along with lots of nice IMDs, only to dissipate 99% of it in a
resistor.  Also not weird using a single IF port rather than separate
TX/RX sockets.

All this in a £700 transverter which doesn't even have a local oscillator.

Two choices then: Build a very linear but pointless 144MHz PA and
control system to warm up a resistor, or whip the lid off the new
transverter and void yet another warranty by swapping out the dropper
resistor.  Either way I still have to add an unwanted IF changeover
relay.  I have serious misgivings about using the Kuhne kit in my 24G
project at all.  All my other transverters apart from the 13cm one have
been butchered to run separate IF tx/rx, (and even that has had the
attenuator modified) or are Kuhnes already equipped with low-level inputs.

Am I the one who is out of step here, or are they stuck in the era where
an FT-817 (or IC-202?) was the state of the art for IF radios?

Neil G4DBN


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